A SAPO-35 molecular sieve, its synthesis method and application

Abstract

This invention discloses a SAPO-35 molecular sieve, its synthesis method, and its applications, belonging to the field of molecular sieve technology. The anhydrous chemical composition of the molecular sieve is: mDMIPA·(Si x Al y P z O2; wherein, the DMIPA is N,N-dimethylisopropylamine; m is per mole (Si x Al y P z The molar number of DMIPA in O2, m = 0.05–0.3; x represents the molar fraction of Si, x = 0.05–0.35; y represents the molar fraction of Al, y = 0.35–0.55; z represents the molar fraction of P, z = 0.25–0.45, and x + y + z = 1. The silica-alumina phosphate molecular sieve SAPO-35 synthesized in this invention can be used as a catalyst for acid-catalyzed reactions, such as a methanol-to-olefins (MTO) catalyst.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve technology, and in particular to a SAPO-35 molecular sieve, its synthesis method, and its application. Background Technology

[0002] SAPO-n molecular sieves are an important class of inorganic microporous materials with significant applications in gas adsorption, separation, and industrial catalysis. Of the 255 existing molecular sieve topologies, over 40 contain an aluminosilicate phosphate composition. Compared to aluminosilicate molecular sieves with the same topology, SAPO molecular sieves exhibit more suitable and tunable acidity and better hydrothermal stability, attracting widespread attention from researchers in recent years.

[0003] SAPO-35 (LEV topology) is one of the important SAPO molecular sieves. This small-porous material Composed of LEV cages connected by single six-membered rings (S6R) and double six-membered rings (D6R), its suitable pore structure exhibits excellent performance in catalysis and gas adsorption separation.

[0004] SAPO-35 molecular sieves are typically synthesized via a hydrothermal method. Currently, the primary template agent used in the synthesis of SAPO-35 molecular sieves is hexamethyleneimine (J. Catal. 2017, 352, 191), but other agents include cyclohexylamine, choline cations, N-methyldiethanolamine, 1-methyl-4-piperidinemethanol (Cryst. Res. Technol. 1993, 28, 1101), and N-methylpiperidine (Natl. Sci. Rev. 2022, 9, nwac094). The choice of structure-directing agent influences the microstructure, elemental composition, chemical environment distribution, and crystal morphology of the synthesized molecular sieve product, thereby affecting its chemical properties. Therefore, developing novel template agents for the synthesis of SAPO-35 molecular sieves is crucial for controlling their catalytic and adsorption separation performance. Summary of the Invention

[0005] In view of this, the present invention provides a SAPO-35 molecular sieve, its synthesis method and application, the main purpose of which is to provide a new synthesis method for SAPO-35 molecular sieve so as to easily control the crystal morphology, composition and properties.

[0006] On one hand, the present invention provides a SAPO-35 molecular sieve, wherein the anhydrous chemical composition of the molecular sieve is: mDMIPA·(Si x Al y P z O2;

[0007] Wherein, the DMIPA is N,N-dimethylisopropylamine;

[0008] m is the number of moles (Si) x Al y P z The number of moles of DMIPA in O2, m = 0.05–0.3;

[0009] x represents the mole fraction of Si, x = 0.05 to 0.35.

[0010] y represents the mole fraction of Al, y = 0.35 to 0.55.

[0011] z represents the mole fraction of P, z = 0.25 to 0.45, and x + y + z = 1.

[0012] Optionally, x is selected from any value among 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35 or a range of values ​​between any two.

[0013] Optionally, y is selected from any value of 0.35, 0.40, 0.45, 0.50, 0.55 or a range of values ​​between any two.

[0014] Optionally, z is selected from any value of 0.25, 0.30, 0.35, 0.40, 0.45 or a range of values ​​between any two.

[0015] Optionally, the X-ray diffraction pattern of the SAPO-35 molecular sieve includes X-ray diffraction peaks at least at the positions shown in the table below:

[0016] No. 2θ 1 8.64 2 10.93 3 11.59 4 13.41 5 17.31 6 17.76 7 20.91 8 21.98 9 23.33 10 27.01 11 28.41 12 32.27 .

[0017] Secondly, the present invention provides a method for preparing the above-mentioned nano-high silica SAPO-35 molecular sieve, comprising the following steps:

[0018] S1: Deionized water, silicon source, aluminum source, phosphorus source and N,N-dimethylisopropylamine are mixed to obtain the initial gel mixture;

[0019] S2: The initial gel mixture undergoes a hydrothermal reaction under sealed conditions. After complete crystallization, the product is separated, washed, and dried to obtain nano-high silica SAPO-35 molecular sieve.

[0020] Optionally, in step S1, the silicon source is calculated as SiO2, the aluminum source as Al2O3, and the phosphorus source as P2O5, and the molar ratio of the components is:

[0021] SiO2 / Al2O3 = 0–1.5;

[0022] P2O5 / Al2O3 = 0.5–1.5;

[0023] H2O / Al2O3 = 10~200;

[0024] DMIPA / Al2O3 = 0.5–8; DMIPA is N,N-dimethylisopropylamine.

[0025] Optionally, DMIPA / Al2O3 = 1.0 to 5; preferably 1.3 to 3.0.

[0026] Optionally, the H2O / Al2O3 ratio is 20 to 200; preferably 20 to 100, and even more preferably 30 to 80.

[0027] Optionally, SiO2 / Al2O3 is selected from any value or a range between any two of 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, and 1.5; preferably 0.1 to 1.0.

[0028] Optionally, P2O5 / Al2O3 is selected from any value of 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or a range between any two.

[0029] Optionally, H2O / Al2O3 is selected from any value or a range between 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, and 200.

[0030] Optionally, DMIPA / Al2O3 is selected from any value of 0.5, 1, 1.5, 2.0, 2.5, 3.0, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8 or a range between any two.

[0031] Optionally, in step S2, the hydrothermal reaction temperature is 130–220°C, and crystallization is carried out under autogenous pressure for 5–72 hours.

[0032] Optionally, the temperature of the hydrothermal reaction is selected from any value or a range between 130, 140, 150, 160, 170, 180, 190, 200, 210, and 220°C; preferably 140-220°C, and more preferably 160-200°C.

[0033] Optionally, the crystallization time is selected from any value or a range between any two of 5, 7, 10, 13, 15, 18, 20, 22, 25, 28, 30, 35, 40, 45, 50, 55, 60, 65, 70, and 72 hours; preferably 20 to 48 hours.

[0034] Optionally, in step S1, the aluminum source is selected from at least one of aluminum nitrate, activated alumina, aluminum hydroxide, aluminum isopropoxide, and boehmite.

[0035] Preferably, in step S1, the phosphorus source is selected from at least one of orthophosphoric acid, ammonium hydrogen phosphate, diammonium hydrogen phosphate, diammonium dihydrogen phosphate, diethyl trichloromethylphosphonate, and phosphorus-containing oxides.

[0036] Preferably, in step S1, the silicon source is selected from at least one of organosilicon, amorphous silica, silica sol, silica gel, silica gel, diatomaceous earth, and water glass.

[0037] Optionally, in step S3, the crystallization process is carried out under static or dynamic conditions.

[0038] Thirdly, the present invention provides an acid catalyst, wherein the product obtained by calcining the SAPO-35 molecular sieve prepared by the above method or the SAPO-35 molecular sieve in air at 400-800°C is the acid catalyst.

[0039] Fourthly, the present invention provides a catalyst for the conversion of oxygen-containing compounds into olefins. The product obtained by calcining the SAPO-35 molecular sieve or the SAPO-35 molecular sieve prepared by the above preparation method in air at 400-800°C is the acid catalyst.

[0040] Fifthly, the present invention provides the application of the above-described SAPO-35 molecular sieve or the SAPO-35 molecular sieve prepared by the above-described preparation method or the above-described acid catalyst in the conversion of oxygen-containing compounds to olefins.

[0041] In a sixth aspect, the present invention provides a method for producing olefins from methanol, the method comprising: calcining a catalyst and then loading it into a reactor and activating it with nitrogen gas at 500–600°C for 0.5–1.5 h; and reacting methanol at 400–500°C to produce olefins; wherein the catalyst is the aforementioned nanoscale catalyst.

[0042] In a seventh aspect, the present invention provides a method for methanol-to-olefins, the method comprising: crushing a molecular sieve, calcining it at a temperature of 550–650°C by introducing air for 2–6 hours, loading the calcined molecular sieve as a catalyst into a reactor, activating it at 500–600°C by introducing nitrogen for 0.5–1.5 hours, and then cooling it to 400–500°C, wherein the reaction raw material methanol is carried by nitrogen, and the reaction produces olefins; wherein the molecular sieve is the above-mentioned SAPO-35 molecular sieve or the SAPO-35 molecular sieve prepared by the above-mentioned preparation method.

[0043] Compared with the prior art, the present invention has the following technical effects:

[0044] (1) The present invention provides a SAPO-35 molecular sieve containing N,N-dimethylisopropylamine.

[0045] (2) This invention provides a method for synthesizing SAPO-35 molecular sieves, which is simple, easy to operate, and suitable for large-scale industrial production.

[0046] (3) The SAPO-35 molecular sieve prepared in this invention exhibits excellent catalytic performance in the conversion of methanol or dimethyl ether into low-carbon olefins. Attached Figure Description

[0047] Figure 1 The X-ray diffraction pattern of the SAPO-35 sample prepared in Example 2 of this invention;

[0048] Figure 2 A scanning electron microscope image of the SAPO-35 sample prepared in Example 1 of this invention;

[0049] Figure 3 The SAPO-35 sample prepared in Example 3 of this invention 13 C solid NMR spectrum. Detailed Implementation

[0050] The present invention is further illustrated below with reference to embodiments, but the present invention is not limited to these embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise specified, the raw materials used in this application are all purchased commercially and used directly without special treatment.

[0051] The analysis method in the embodiments of this application is as follows:

[0052] X-ray powder diffraction (XRD) phase analysis was performed using an X'Pert PRO X-ray diffractometer from PANalytical, Netherlands, with a Cu target, Kα radiation source (λ = 0.15418 nm), voltage 40 kV, and current 40 mA.

[0053] The scanning electron microscope (SEM) used for testing was a Hitachi SU8020 field emission scanning electron microscope with an accelerating voltage of 2kV.

[0054] In the examples, the bulk elemental composition was determined using a Philips Magix 2424 X-ray fluorescence analyzer (XRF).

[0055] The NMR of the samples was measured using a Bruker Avance III 600 (14.1Tesla) spectrometer. 13 The resonant frequency of C is 150.9 MHz. 13 The CM-MAS NMR experiment was conducted using a 4mm triple resonance probe with a contact time of 3ms, an experimental rotation speed of 12kHz, a sampling delay of 2s, and a chemical shift reference correction of 0ppm using adamantane.

[0056] Examples 1-7 (Synthesis of SAPO-35 molecular sieves)

[0057] The synthesis method and results of SAPO-35 are shown in Table 1. First, an aluminum source was dissolved in water, followed by the addition of an optional phosphorus source, silicon source, and N,N-dimethylisopropylamine (R). After thorough mixing at room temperature, the gel was transferred to a stainless steel reactor. The reactor was placed in an oven, heated to 140-220℃, and reacted for a certain time before cooling to complete crystallization. The solid product was centrifuged, washed, and dried in air at 120℃ to obtain the molecular sieve powder sample. XRD, SEM, and XRF analyses were performed on the synthesized sample.

[0058] Table 1 Synthesis conditions and results of molecular sieves 1-7

[0059]

[0060] Phase, morphology and composition analysis were performed on the seven samples prepared in Examples 1 to 7:

[0061] The samples from Examples 1-7 were characterized by XRD powder diffraction, and the results showed that all samples exhibited characteristic diffraction peaks of SAPO-35, confirming that they are LEV crystalline phases. Taking Example 2 as an example, the XRD diffraction pattern of the obtained sample is shown below. Figure 1 As shown. The peak positions and shapes of the XRD spectra of samples 1, 3-7 are the same as those in Example 2, except that there is a fluctuation of about 10% in peak intensity.

[0062] Inorganic composition analysis of samples 1-7 was performed using XRF. The results are shown in the product composition column of Table 1, as follows: Al 0.47 Si 0.16 P 0.37 O2, Al 0.46 Si 0.20 P 0.34 O2, Al 0.49 Si 0.13 P 0.38 O2, Al 0.46 Si 0.13 P 0.41 O2, Al 0.49 Si 0.04 P 0.47O2, Al 0.49 Si 0.07 P 0.44 O2, Al 0.50 Si 0.07 P 0.43 O2.

[0063] SEM analysis of synthesized samples 1-7 revealed similar micron-sized prismatic crystals. For example, the SEM image of Example 1 is shown below. Figure 2 The sample from Example 3 was subjected to... 13 CMAS NMR solid-state NMR analysis, such as Figure 3 As shown, the characteristic peaks of N,N-dimethylisopropylamine are indeed present in the sample.

[0064] Table 2. X-ray diffraction peak data of SAPO-35-2 in Example 2

[0065] No. 2θ 1 8.64 2 10.93 3 11.59 4 13.41 5 17.31 6 17.76 7 20.91 8 21.98 9 23.33 10 27.01 11 28.41 12 32.27

[0066] Application Example 1 (MTO Catalytic Reaction)

[0067] The low-silicon SAPO-35-6 molecular sieve prepared in Example 6 was first pressed into tablets and crushed to 20-40 mesh, then calcined at 600°C with air for 4 hours. 0.3 g of this sample was then loaded into a self-made fixed-bed reactor (a quartz tube reactor) as a catalyst for MTO reaction evaluation. The reactor was activated at 550°C with nitrogen for 1 hour, then cooled to 450°C for the reaction. Methanol was carried by nitrogen gas at a methanol space velocity (MSH) of 2 h⁻¹. -1 The reaction products were analyzed by online gas chromatography (Agilent A7890) using a PoraPlot-Q-HT column, and the results are shown in Table 3.

[0068] Table 3. MTO catalytic performance of the synthesized samples a

[0069]

[0070] a Reaction conditions: 450℃, methanol space velocity 2h -1 Lifetime is defined as the length of time during which methanol conversion is greater than 99%, and selectivity is given when the selectivity of ethylene plus propylene is highest.

[0071] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A SAPO-35 molecular sieve, characterized in that, The anhydrous chemical composition of the molecular sieve is: m DMIPA·(Si x Al y P z O2; Wherein, the DMIPA is N,N-dimethylisopropylamine; m is per mole (Si) x Al y P z The number of moles of DMIPA in O2, m = 0.05 ~ 0.3; x represents the mole fraction of Si, x = 0.30~0.

35. y represents the mole fraction of Al, y = 0.35 ~ 0.

55. z represents the mole fraction of P, z = 0.25~0.45, and x+y+z = 1; The molecular sieve preparation method includes the following steps: S1: Deionized water, silicon source, aluminum source, phosphorus source and N,N-dimethylisopropylamine are mixed to obtain the initial gel mixture; S2: The initial gel mixture undergoes a hydrothermal reaction under sealed conditions. After complete crystallization, the product is separated, washed, and dried to obtain nano-high silica SAPO-35 molecular sieve. In step S1, the silicon source is calculated as SiO2, the aluminum source as Al2O3, and the phosphorus source as P2O5, and the molar ratio of the components is: SiO2 / Al2O3 = 0~1.5; P2O5 / Al2O3 = 0.5~1.5; H2O / Al2O3 = 10~200; DMIPA / Al2O3 = 0.5~8; DMIPA is N,N-dimethylisopropylamine.

2. The SAPO-35 molecular sieve according to claim 1, characterized in that, The X-ray diffraction pattern of the SAPO-35 molecular sieve includes X-ray diffraction peaks at at least the positions shown in the table below: 。 3. The method for preparing SAPO-35 molecular sieve according to any one of claims 1 to 2, characterized in that, The preparation method includes the following steps: S1: Deionized water, silicon source, aluminum source, phosphorus source and N,N-dimethylisopropylamine are mixed to obtain the initial gel mixture; S2: The initial gel mixture undergoes a hydrothermal reaction under sealed conditions. After complete crystallization, the product is separated, washed, and dried to obtain nano-high silica SAPO-35 molecular sieve.

4. The method for preparing SAPO-35 molecular sieve according to claim 3, characterized in that, In step S1, the silicon source is calculated as SiO2, the aluminum source as Al2O3, and the phosphorus source as P2O5, with the following molar ratio: SiO2 / Al2O3 = 0~1.5; P2O5 / Al2O3 = 0.5~1.5; H2O / Al2O3 = 10~200; DMIPA / Al2O3 = 0.5~8; DMIPA is N,N-dimethylisopropylamine.

5. The method for preparing SAPO-35 molecular sieve according to claim 4, characterized in that, DMIPA / Al2O3=1.0~5; H2O / Al2O3=20~200.

6. The method for preparing SAPO-35 molecular sieve according to claim 4, wherein DMIPA / Al2O3 = 1.3~3.0; H2O / Al2O3 = 20~80.

7. In the preparation method of SAPO-35 molecular sieve according to claim 4, in step S2, the hydrothermal reaction temperature is 130~220 ºC, and crystallization is carried out under autogenous pressure for 5~72 hours.

8. In the method for preparing SAPO-35 molecular sieve according to claim 4, in step S2, the temperature of the hydrothermal reaction is 140~220 ºC.

9. In the method for preparing SAPO-35 molecular sieve according to claim 4, in step S2, the temperature of the hydrothermal reaction is 160~200 ºC.

10. The method for preparing SAPO-35 molecular sieve according to claim 4, characterized in that, In step S1, the aluminum source is selected from at least one of aluminum nitrate, activated alumina, aluminum hydroxide, aluminum isopropoxide, and boehmite. In step S1, the phosphorus source is selected from at least one of orthophosphoric acid, ammonium hydrogen phosphate, diammonium hydrogen phosphate, diammonium dihydrogen phosphate, diethyl trichloromethylphosphonate, and phosphorus-containing oxides. In step S1, the silicon source is selected from at least one of organosilicon, amorphous silica, silica sol, silica gel, silica fume, diatomaceous earth, and water glass.

11. The method for preparing SAPO-35 molecular sieve according to claim 3, characterized in that, In step S1, the crystallization process is carried out under static or dynamic conditions.

12. An acid catalyst, characterized in that, The product obtained by calcining the SAPO-35 molecular sieve according to any one of claims 1 to 2 or the SAPO-35 molecular sieve prepared by any one of claims 3 to 11 in air at 400 to 800 °C is the acid catalyst.

13. The application of the SAPO-35 molecular sieve according to any one of claims 1 to 2, or the SAPO-35 molecular sieve prepared by the preparation method according to any one of claims 3 to 11, or the acid catalyst according to claim 12, in the reaction of converting oxygen-containing compounds to olefins.

14. A method for producing olefins from methanol, characterized in that, The method includes: crushing the molecular sieve, calcining it at 550~650℃ with air for 2~6 hours, loading the calcined molecular sieve into a reactor as a catalyst, activating it with nitrogen at 500~600℃ for 0.5~1.5 hours, and then cooling it to 400~500℃. The reaction raw material methanol is carried by nitrogen, and the reaction produces olefins. The molecular sieve is the SAPO-35 molecular sieve according to any one of claims 1~2 or the SAPO-35 molecular sieve prepared by the preparation method according to any one of claims 3~11.

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